Aluminum chloride production process

ABSTRACT

Multicourse liner construction for a fluidized bed reaction chamber for the chlorination of alumina bearing material including a reaction-chamber-defining inner course of essentially non-reactive carbon, an outer course of heat insulating refractory material, and an intermediate course of high density and essentially non-reactive material to minimize undesired flow of reactant chlorine externally of said reaction chamber.

This application is a continuation of application Ser. No. 423,808 filedDec. 11, 1973, now U.S. Pat. No. 3,959,439 issued May 25, 1976, whichapplication was a continuation-in-part of our earlier application Ser.No. 180,373 filed Sept. 14, 1971, now U.S. Pat. No. 3,796,551 issuedMarch 12, 1974.

The present invention relates to an improved construction for afluidized bed reaction chamber for the large scale economic productionof aluminum chloride by the chlorination of aluminous material.

Although the potential advantages of utilizing aluminum chloride as asource material in the electrolytic production of aluminum have longbeen recognized, commercial realization thereof has been precluded bythe inability of the art both to provide aluminum chloride ofsufficiently high purity as to be utilizable therein and to providealuminum chloride in any significant required quantity therefor in aneconomically acceptable manner. The long standing incentive and need foreconomically producible high purity aluminum chloride has resulted inextensive experimental exploration and evaluation of numerous suggestedexpedients for obtaining such long desired result. However, to date noneof these suggested expedients has succeeded in satisfying the desiredobjective of commercial quantity production of economically produciblehigh purity aluminum chloride.

Among the many problems attendant the economic, large quantityproduction of high purity aluminum chloride is the provision of along-lived fluidized bed reaction chamber for the chlorination reactionthat can both minimize the passage of unreacted chlorine valuestherethrough and can effectively withstand the highly penetrant actionof corrosive chlorine at elevated temperatures for extended periods oftime without utilization of materials that will deleteriously effect thebasic reaction or undesirably contaminate the resultant product.

This invention may be briefly described as an improved construction fora long-lived fluidized bed reaction chamber for the continuousproduction of aluminum chloride by the conversion of aluminous materialsin the presence of both chlorine and carbon values that minimizes if noteffectively avoids, exposure of the bed contents to deleteriouscontaminants and the passage of unreacted chlorine values therethroughand which also effectively precludes deleterious seepage of the highlypenetrant, high temperature chlorine values through the chamber liningto extend the operable life thereof. In its broader aspects the subjectinvention includes the provision of a composite multicourse,multifunctional lining for a fluidized bed reaction chamber for thecontinuous production of aluminum chloride for extended periods of timeby the chlorination of alumina-bearing material in the presence ofreductant carbon values.

Among the advantages of the subject invention is the provision of areaction chamber of extended operating life for the continuous economicformation of aluminum chloride by the chlorination of aluminous materialin the presence of reductant carbon values.

Still other advantages include the provision of a reaction chamberlining construction for production of aluminum chloride that minimizesexposure of the reaction constituents to deleterious contaminants, andeffectively precludes penetration of the lining by the highly corrosiveand highly penetrant chlorine values in the reaction mixture.

The object of this invention is the provision of an improvedconstruction for a fluidized bed reaction chamber for the chlorinationof aluminous material in the presence of reductant carbon values.

Other and further objects of the invention will become apparent from thefollowing portions of this specification and from the accompanyingdrawing which, in accord with the mandate of the statute, illustratesthe principles of the invention as embodied in a presently preferredembodiment thereof.

Referring to the drawing:

The sole FIGURE is a schematic vertical sectional view of a fluidizedbed reaction chamber constructed in accord with the principles of thisinvention.

The production of aluminum chloride by the chemical interaction ofaluminous materials with chlorine and carbon values has been long knownto the art. Among the many expedients explored by the art in attemptingto attain the long sought objective of high quantity, economicproduction of high purity aluminum chloride are the use of diversealuminous or alumina bearing materials such as various clays, bauxiteand different types of alumina and the use of diverse forms of carbonand chlorine, include composite forms thereof, such as phosgene. Recentdevelopments have indicated however that a preferred reaction for theeconomic, high quantity production of aluminum chloride comprises thechlorination of carbon impregnated alumina of selective character.Operations associated therewith have also indicated the necessity ofpreventing the introduction of contaminants into the reaction mixturewhile maintaining the reaction continuity for extended periods of timein the presence of highly corrosive and highly penetrating hightemperature chlorine as significant parameters in the attaining of thelong sought objective of high quantity production of high purityaluminum chloride. To the above ends, the subject invention isparticularly directed to an improved construction for a fluidized bedreaction chamber for the extended and continuous chlorination of aluminafor the production of high purity aluminum chloride.

Referring to the drawing, there is illustrated a fluidized bed reactionchamber 1 for the production of aluminum chloride constructed in accordwith the principles of this invention and broadly constituted of anexternal metal shell 2 and a selectively constituted multicourse liningdefining a generally cylindrically shaped reaction zone 3 therewithin.

The multicourse lining comprises an outer course 4 disposed adjacent tothe metal shell 2, a multilayered inner course 6 disposed in spacedrelation with said outer course 4 and peripherally confining thereaction zone and an intermediate course 5 of compacted selectivelyconstituted particulate material.

The inner course 6 is formed of a plurality of layers of stacked blocksof essentially reaction inert and non-contaminating material, preferablybaked carbon of a character like that employed as anode material inaluminum electrolytic reduction cells using "prebaked" anodes (ascontrasted with Soderberg anodes). Appropriate techniques for producingbaked anode blocks are set forth in U.S. Pat. No. 3,009,863 for "Methodsfor Thermally Processing Carbon Articles" and on pages 38 to 40 of "TheChemical Background of the Aluminum Industry" by T. G. Pearson,Lectures, Monographs and Reports, 1955, No. 3, The Royal Institute ofChemistry, London, England. By "reaction inert", I intend to encompasslining materials that are essentially free of any tendency to react withthe reagents and the reaction products present in the reaction chamberor to deteriorate under the conditions of the reaction. Such bakedcarbon material is also basically of the same chemical element, i.e.carbon, as at least one of the reaction components and hence, even if itdeteriorates slightly under the reaction conditions, it will not becontaminating. The described usage of stacked blocks inherently providesinterstices at the interfaces therebetween, and the inherent presenceand accommodation thereof according to the present invention avoids thedeteriorative effects that normally result from the presence of inducedcracks in monolithic lining structures.

The outer course 4 disposed adjacent to the metal shell 2 is made up ofone or more layers of heat insulating material, suitably conventionalsilica, alumina, or aluminasilica refractory brick low in titanium andiron, such as "Vegalite" of Harbison-Walker Refractories Co.,Pittsburgh, "Alfrax" of the Carborundum Co., Niagara Falls, and"Sil-O-Cel Super" of Johns-Manville, New York.

The intermediate course 5 is formed of reaction inert and desirablynon-contaminating particulate material that is disposed in suchcompacted condition as to provide a predetermined degree of resistanceto the passage of penetrant gaseous material therethrough. Suchintermediate course 5 is preferably formed of particles of alumina thathave been heated sufficiently, preferably to alpha alumina, to reducetheir possible reactivity with gases extant within or emanating from thereaction chamber and to concomitantly maximize the density thereof. Suchhigh density particles, preferably of a particle size rangecharacterized in that all of the particles are below 325 mesh (U.S.Sieve Series), are disposed intermediate the inner and outer courses incompacted condition such as to provide a bulk density of at least about120 pounds per cubic foot and, preferably, 140 pounds per cubic foot.Such compacted alpha alumina, although of such markedly limitedreactivity as to be practically reaction-inert as compared to thereaction alumina employable in the reaction chamber, is neverthelessalso of essentially the same chemical composition as the reactionalumina and hence is also inherently non-contaminating in character. Theinherent high density of the particles and the high bulk density of thecourse 5 operates to effectively seal the interface at the inner face ofthe stacked blocks of the inner course 6 and to pack the intersticesextant thereat and to constitute a barrier layer that provides aresistance to gas flow therethrough, both transversely andlongitudinally across each vertical tier of blocks, that is appreciablygreater in magnitude than that extant in the zone 3 intermediate theinlet and outlet of the reaction chamber. The maintenance of suchcomparatively high resistance to flow of highly penetrant and highlycorrosive gases extant within the reaction chamber, usually chlorine gasor gas containing chlorine values, both transversely through theintermediate course 5 toward the metal shell 2 and longitudinallythereof across each vertical tier of blocks of the inner course 5 meansthat the chlorine cannot bypass the chlorination reaction zone andresults not only in high efficiency utilization of chlorine but alsomarkedly extends the operating life of the chamber.

According to the preferred embodiment, there is interposed between theintermediate course 5 and the outer course 4 a lining course 7constructed likewise of baked carbon anode block. Its purpose is toprotect the refractory brick of outer course 4 from any chlorine orphosgene which might leak through intermediate layer 5. Likewise, sincemost of the chlorine values have reacted to form aluminum chloride bythe time the fluidizing gases leave the top of the fluidized bed, it ispossible to have the intermediate course 5 only extend at least to thelevel of the top of the fluidized bed. It is, for example, possible inan alternative embodiment to extend inner course 6 and intermediatecourse 5 only as high as the level of the top of the fluidized bed andthen provide lining course 7 in the form of more massive anode blocks,this course 7 extending upwards to support the dome of the chamber.

The bottom of the fluidized bed chamber comprises a gas distributioninlet assembly, generally designated 12, for effecting the controlledintroduction of reactant gas containing chlorine or chlorine valuesthereinto.

Such gas distribution assembly 12 desirably comprises a central,randomly permeable porous gas distribution plate or member 13 foreffecting the introduction of a central gas stream of selective diffusecharacter and crosssection to fluidize a particulate bed of aluminous oraluminabearing material to be maintained in zone 3 and to reacttherewith. Such distribution member 13 is preferably mounted in asupporting ring 19 and additionally serves as a removable manhole coverfor access to the interior of the vessel. The main gas distribution body13 is preferably in the form of a block or plate of porous silica havingan appreciable thickness or depth relative to its crosssection dimensionand is centrally disposed in the chamber. The described randomly porousgas distribution plate operatively functions to provide a myriad ofindividual tortuous gas passages therethrough and effects thesubdivision of the main gas stream into a multiplicity of individualdiscrete streams of diminutive cross-section that compositely constitutethe core stream. Perimetrically disposed about the main gas distributionplate 13 is an annular secondary gas distribution assembly, generallydesignated 14. Such secondary distribution assembly 14 laterallyconfines the main gas flow distribution block 13 and effects issuance ofa perimetric stream of reactant gas in the form of a boundary streamaround the central gas stream and in concurrent direction therewith toadditionally sweep the surface of the inner course of lining 6.

The perimetrically disposed secondary distribution assembly 14 isarranged to provide a composite flow of substantially uniform radialdimension and, for the described circular main distribution block 13,will be generally in the form of a perimetric annulus disposedthereabout. Such assembly 14 may, as shown in the drawing, beconstituted by a plurality of arcuate slots or by a plurality ofindividual nozzles 15 fed through the annulur distributor chamber 16,connected to the main fluidizing reactant gas supply chamber 17 througha plurality of channels 18. In particular, the nozzles 15 areoperatively distributed throughout the crosssectional area of the spacebetween the inner lining course 6 and the periphery of the distributionblock 13, and are preferably surmounted by bubble caps 20 and otherdiffusing means 21 to effect a radial diffusion of the emitted gas andconvert the separately issued streams into a stream of upwardly movinggas. The bubble cap-surmounted nozzles can be composed substantially ofquartz, graphite, alumina, silicon oxynitride, nickel alloys, or thelike, for example, to withstand the vigorous reaction conditions, andespecially the high temperatures which may be generated during theexothermic chlorination reaction to be carried out in the chamber.

In accordance with a preferred feature of the invention, the diffusingmeans 21 comprises a bed of loosely packed porous refractory spheres, asfor example composed substantially of calcined alumina, supported by theplate 22 and loosely packed about the nozzles 15, to insulate thenozzles from the heat generated by the reaction, e.g. the exothermicchlorination of alumina bearing material, and to more uniformlydistribute the emitted gas throughout the operative flow cross-sectionalarea of such nozzle means.

The reactor chamber 1 also includes a gaseous effluent outlet 23 remotefrom the gas distribution inlet for removal of the effluent gases fromthe system, and can have material inlet means schematically shown at 24,of conventional character to permit introduction of other reactants andthe fluidized bed particles.

Although the majority of the length of zone 3 is shown as having acylindrical configuration, it is advantageous that the course 6 taperinwardly upward from the distribution assembly 14 for at least the depthof the fluidized bed, as described in U.S. patent application Ser. No.180,419 of Cook et al., for the purpose of selectively disturbing anddisrupting the upward flow of gas in the vicinity of the side walls toprovide improved gas turbulence and fluidization at the side walls.

In the operation of the described unit, a central stream of chlorine gasmade up of a multiplicity of uniformly distributed individuallyconstituted diffuse gas streams of small cross-sectional extent will beintroduced into the fluidized bed reaction zone 3 through the main gasdistribution plate 13. This central stream will be perimetricallybounded by a concurrent secondary stream of reactant gas serving as aboundary curtain to sweep the face of the inner lining course 6 in thereaction zone.

As will now be apparent to those skilled in this art, the interrelatedphysical and chemical properties of the individual courses making up thedescribed multicourse lining cooperatively function to preclude passageof highly penetrant and corrosive chlorine externally of the reactionchamber through interposition of a selectively constituted barrier ofessentially reaction inert and non-contaminating materials to provide areaction chamber of markedly extended operating life for the productionof high purity aluminum chloride by the chlorination of aluminousmaterial in the presence of reductant carbon therein.

It will be appreciated that the instant specification and drawing areset forth by way of illustration and not limitation, and that variousmodifications and changes may be made without departing from the spiritand scope of the present invention which is to be limited only by thescope of the appended claims.

Having thus described my invention, I claim:
 1. In the production ofaluminum chloride by the chemical interaction of carbon and chlorinevalues with aluminous materialthe improvement comprising introductingsaid chlorine values through a regent inlet to contact said aluminousmaterial within a reaction zone of a reaction chamber having an outletand including (1) a multilayer lining that comprises an inner and gaspermeable lining wall of reaction-inert material, and an intermediatelayer of reactioninert particulate material disposed outwardly of saidinner layer and providing a resistance to gas flow that is greater thanthe resistance to gas flow extant in the reaction zone between the inletand outlet of said reaction chamber to preclude displacement of saidchlorine values through said intermediate layer, and (2) wall meansdisposed outwardly of said intermediate layer and functioning to supportthe outer side of the intermediate layer.